A casing string is typically cemented within a wellbore by pumping cement slurry down, through the casing string and radially-outward from the lower end of the casing string. The cement slurry flows upward within an annulus formed between the casing string the wellbore wall, where it is then allowed to set. When the entire length of the casing string cannot be cemented within the wellbore in this manner, a procedure generally known as “multi-stage cementing” is used.
During multi-stage cementing, the cement slurry is pumped into the annulus between the casing string and the wellbore wall from at least two different locations along the length of the casing string. The first location is typically at the bottom of the casing string, commonly referred to as the first stage cementing position. The second and subsequent (if any) locations or “positions” are between the top and bottom of the casing. One or more additional locations/stages may also be employed.
What is needed is an improved multi-stage cementing tool and methods of use.